Substituted alpha-chloro-methane-sulfenyl chlorides and their manufacture

ABSTRACT

SUBSTITUTED ALPHA-CHLORO-METHANE-SULFENYL CHLORIDES, INTERMEDIARY CHLORINATED BENZYL SULFIDES AND CHLORINATED MERCAPTANS USEFUL AS HERBICIDES AND CHEMICAL INTERMEDIATES FOR HERBICIDES ARE PREPARED BY THE CHLORINATION OF SUBSTITUTED METHYL BENZYL SULFIDES AND SUBSTITUTED METHYL MERCAPTANS.

Patented Apr. 9, 1974 3,803,224 SUBSTITUTED ALPHA-CHLORO-METHANE-SULFENYL CHLORIDES AND THEIR MANUFACTURE Wendell Gary Phillips,Olivette, Mo., assignor to Monsanto Company, St. Louis, M0. N Drawing.Filed May 3, 1971, Ser. No. 139,977 Int. Cl. C07c 145/00 US. Cl. 260-543H Claims ABSTRACT OF THE DISCLOSURE Substitutedalpha-chloromethane-sulfenyl chlorides, intermediary chlorinated benzylsulfides and chlorinated mercaptans useful as herbicides and chemicalintermediates for herbicides are prepared by the chlorination ofsubstituted methyl benzyl sulfides and substituted methyl mercaptans.

This invention relates to substituted alpha-chloro-rnethand theirmanufacture by reaction of chlorine, sulfuryl chloride or mixturesthereof with the corresponding precursors of the formulas RCH:

wherein R is hydrogen or alkyl of from 1 to 3 carbons, E is amino, E isalkoxy, E" is aryl or halogenated aryl, and Z is hydrogen or benzyl.

Preferred amino are represented by the formula Q! wherein Q and Q areeach hydrogen, alkyl of from 1 through 5 carbons, alkoxyalkyl, aryl andhalogenated aryl.

Preferred alkoxy are lower alkoxy of from 1 through 5 carbon atoms. Morepreferred are methoxy, ethoxy, propoxy, isopropoxy, butoxy andsecbutoxy. Still more preferred are methoxy and ethoxy.

Preferred aryls include phenyl, tolyl, dimethylphenyl, ethylphenyl,diethylphenyl, trimethylphenyl, triethylphenyl, propylphenyl, cumenyl,and trihalomethylphenyl. More preferred are phenyl and tolyl. Still morepreferred is phenyl.

Preferred halogenated aryls include halophenyl, dihalophenyl andtrihalophenyl. More preferred are bromophenyl, fluorophenyl,chlorophenyl, dibromophenyl, difluorophenyl, dichlorophenyl andtrichlorophenyl. Still more preferred are chlorophenyl, dichlorophenyland trichlorophenyl.

Examples of amino present in the compounds of the present invention usedin or made by the method of the present invention include, but are notlimited to, amino, methylamino, ethylamino, propylamino, isopropylamino,butylarnino, secbutylamino, methoxymethylarnino, ethoxymethylamino,propoxymethylamino, butoxymethylamino, dirnethylamino, diethylamino,di-isopropylamino, phenyl methoxymethylamino, phenyl ethoxymethylamino,phenyl propoxymethylamino, tolyl methoxymethylamino, halophenylethoxyethylamino and alkyleneamino wherein the alkylene forms acontinuous chain between the terminal valence bonds of the nitrogen atomof from 4 through 8 carbon atoms, as well as anilino, paraalkylanilino,orthoalkylanilino, 2,6-dialkylanilino, 2,4,6-trialkylanilino and3,4,5-trialkylanilino wherein alkyl is methyl, ethyl, isopropyl andtertbutyl and meta-trihalomethylanilino, parahaloanilino,ortho-haloanilino, 2,6 dihaloanilino, 2,4,6-trihaloanilino, and3,4,5-trihaloanilino wherein halo is chloro, bromo or fluoro.

In the overall manufacture of substituted alpha-chloromethane-sulfenylchlorides of this invention from the corresponding precursors, areaction occurs which, while not completely understood in the manner ofits mechanism, can be represented by the following chemical equations,wherein E, E, E", R and Z have the aforementioned significance.

vi rW-ii-cn-s cn as 01012 0 or i i Q E -s-o1+ cmo1+ 21101 aso,

ubnci By controlling the quantity of chlorinating agent, is. chlorine,sulfuryl chloride, or mixtures thereof the above reactions appear toproceed in a stepwise fashion as illustrated by the following chemicalequations.

R HI

the product of Equation vii or the product of Equation ix is the desiredproduct, it is obtained by mixing in an inert organic liquid to efiectevolution of hydrogen chloride, one molecular proportion of precursorsubstituted methyl-benzyl sulfide and about one molecular proportion ofchlorine or sulfuryl chloride (when sulfuryl chloride is employedinstead of chlorine in Whole or in part sulfur dioxide also evolves as abyproduct along with by-product hydrogen chloride) at a temperatureabove the freezing point of the system. The said intermediary product isreadily isolated from this reaction mass, as for example by evaporationof the inert organic liquid and recrystallization of the residue in thecold to give the intermediate product. The yield of the saidintermediary is generally one hundred percent, but declines as thereaction temperature increases above the range of from about 25 C. toabout 30 C., the formation of benzyl chloride being observed. Since thechlorination appears to proceed in a step-wise fashion, the intermediaryproduct may likewise be obtained even when the chlorinating agent ispresent in quantities greater than the stoichiometric amount so long asreaction conditions are very mild; i.e., the temperature is maintainedbelow 20 degrees centigrade and reaction time does not exceed about onehour.

In the overall process of this invention for the preparation ofsubstituted alpha-chloro-methane-sulfenyl chlorides, as represented byEquations i through vi, the chlorinating agent may be chlorine alone,sulfuryl chloride alone, or a mixture of any proportion of chlorine andsulfuryl chloride. The chlorinating agent may be present in excess andthe reaction may be carried out at any temperature from above thefreezing point of the system to about the boiling point of the system atthe desired pressure under which the reaction is conducted.

Since gaseous reaction products are evolved the reaction is usuallycarried out at atmospheric pressure but higher or lower pressures may beutilized if equipment and other factors favor such higher or lowerpressures. The reaction may be carried out in an open vessel or underreflux.

It is preferable to conduct the reaction in the presence of an inertorganic liquid but when reaction conditions are mild, i.e. the reactionis conducted at a temperature below about 70 degrees centigrade, anexcess of sulfuryl chloride may perform the solvating function of theinert organic liquid and there is no necessity for the inert liquid inthe reaction system. In a preferred embodiment of the process for thepreparation of substituted alpha-chlorornethane-sulfenyl chloride in thepresence of an inert organic liquid there will be employed for each moleof precursor substituted methylbenzyl sulfide or substituted methylmercaptan from 2 to 6 moles of chlorine or sulfuryl chloride or mixturethereof. The reaction is preferably carried out at a temperature abovethe freezing point of the system but below the boiling of the inertorganic liquid. More preferably the reaction is carried out attemperatures of from about 0 degree Centigrade to about degreescentigrade and still more preferably from about 0 to about 70 degreescentigrade.

Prescursor amide-substituted methyl merca-ptans are readily obtainableby initially slowly mixing at about room temperature one molecularproportion of an appropriate amine, substituted amine, aniline orsubstituted aniline, EH, With an acid,

selected to give the desired substituted methyl mercaptan,

H l s RCHz-(JHi'B-E thereafter refluxing for from about 3 to about 6hours, cooling the mass to about room temperature, separating themercaptan from the cooled mass by conventional means, washing themercaptan with a dilute aqueous acid solution and, if necessary,recrystallizing or distilling the prod uct to purify same.

Precursor carbalkoxy-substituted methyl mercaptans are readilyobtainable by initially slowly mixing at about room temperature onemolecular proportion of an appropriate alcohol, E'H, with an acid,

H l S l RCHZ-dHd-OH selected to give the desired substituted methylmercaptan,

l s o thereafter refluxing in the presence of an excess of the alcoholin an acidic medium for from about 1 to 3 hours, cooling the mass toabout room temperature, stripping oil" the excess alcohol, and, ifnecessary, recrystallizing or distilling the product to purify same.

Precursor substituted methyl benzyl sulfides are readily obtainable byinitially slowly mixing at about room temperature one molecularproportion of a substituted alphahalo-alkyl-carbonyl,

wherein X is halo, corresponding to the desired substitutedmethyl-benzyl sulfide with an aqueous solution containing one molecularproportion of benzyl mercaptan and one molecular proportion of sodiumhydroxide, thereafter refluxing the so-charged mass for about twelvehours, cooling to about room temperature, extracting the cooled masswith methylene chloride, and then separating the product by evaporatingmethylene chloride from the extract, and if necessary, vacuum distillingthe product to purify same.

The inert organic liquid employed in the overall manufacture of thisinvention or any portion thereof can be any organic liquid, or mixturesthereof, which is inert under the reaction conditions, and preferablythat having a boiling point in the range of from about 30 C. to about100 C. Ordinarily, the inert organic liquid comprises liquid alkanes orliquid chloroalkanes or various mixtures thereof, for example; pentane,3-ethylpentane, hexane, Z-ethylhexane, heptane, dichloromethane,1,1-dichloroethane, chloroform, carbon tetrachloride, isobutyl chloride,and various mixtures thereof. In general it is preferable, but notnecessary, that the amount of said inert organic liquid presentthroughout the course of the reaction be that at least suflicient tomaintain the intermediary alpha-chloromethyl-benzyl sulfide in solution.Where the reactions are carried out in step-wise fashion in proceedingfrom intermediary alpha-chloromethylbenzyl sulfides to analphachloro-alpha-(chloromercapto)-compound the inert organic liquidwill usually be the same as that employed in preparing the intermediaryor intermediaries; however, such can be replenished or replaced in wholeor in part by a different inert organic liquid in any or each step.

In the matter of pressure, either that above or below atmosphericpressure can be employed, however, in general atmospheric pressure willbe satisfactory.

Substituted alpha-chloro-methane-sulfenyl chlorides exhibit herbicidalactivity toward noxious Weeds and have particular utility as selectivepre-emergent herbicides.

As illustrative of this invention but not limitative thereof is thefollowing.

EXAMPLES 1 THROUGH 4 These examples illustrate the preparation ofsubstituted methyl mercaptans having the formulas which mercaptans areprecursors to the compounds of the present invention.

EXAMPLE 1 To a suitable reaction vessel equipped with a thermometer,agitator and venting means are charged approxi mately 65 parts by weightof ortho-chloroaniline (about /2 mole) and approximately 53 parts byweight of thiolactic acid (about V2 mole). The contents of the sochargedvessel are heated with agitation under a nitrogen atmosphere to about130 degrees centigrade and maintained at that temperature for about 4hours. The contents are cooled to about room temperature and washed witha dilute aqueous HCl solution. A white solid is isolated by filtration,dissolved in and recrystallized from chloroform, and identified asalpha-mercapto-ortho-chloropropanilide (melting point of 83 to degreescentigrade).

Alpha mercapto-alpha-methyl-ortho-chloropropanilide exhibitspre-emergent herbicidal activity against morning glory and Johnsongrass.

EXAMPLE 2 The procedure of Example 1 is followed except that in place of65 parts by weight of ortho-chloroaniline an equimolecular proportion ofaniline is charged to the vessel. Alpha-mercaptopropanilide is obtained.

In similar fashion other ring substituted alpha-mercapto-propanilidesmay be prepared from the appropriate substituted aniline. Likewise, bycharging to the reactor in place of the thiolactic acid an equalmolecular proportion of higher acids in the thiolactic acid seriessubstituted alpha-acetanilido substituted methyl mercaptans having theformula wherein R is methyl, ethyl, propyl and isopropyl may beprepared.

EXAMPLE 3 The procedure of Example 1 is followed except that in place of65 parts by weight of ortho-chloroaniline an equimolecular proportion ofdiethyl amine is charged to the vessel.N,N-diethyl-alpha-mercapto-propionamide is obtained.

In similar fashion other N-substituted alpha-mercapto-propionamides maybe prepared from the appropriate N-substituted amide. Likewise, bycharging to the reactor in place of the thiolactic acid an equalmolecular proportion of higher acids in the thiolactic acid series substituted alpha-amido-substituted methylmercaptans having the formulawherein R is methyl, ethyl, propyl and isopropyl may be prepared.

EXAMPLE 4 To a suitable reaction vessel equipped with a thermometer,agitator and venting means are charged approximately 500 parts by weightof isopropyl alcohol and approximately 53 parts by weight of thiolacticacid (about /2 mole). To the so-charged mass is added about 1 part byweight of concentrated H 50 The contents of the so-charged vessel areheated with agitation under a nitrogen atmosphere to reflux temperatureand maintained ORH:

wherein R is methyl, ethyl, propyl and isopropyl may be prepared.

EXAMPLES AND 6 These examples illustrate the preparation of substitutedmethyl benzyl sulfides having the formulas ORB:

and

which sulfides are precursors to the compounds of the present invention.

EXAMPLE 5 To a suitable reaction vessel equipped with a thermometer andagitator charged with an aqueous solution containing approximately 200parts by weight of water and approximately parts by weight of sodiumhydroxide is added with agitation approximately 62 parts by weight ofbenzyl mercaptan. Thereafter approximately 91 parts by weight of ethylalpha-bromo-propionate is added with agitation. Thereupon the mass isagitated at room temperature for about one hour. Thereafter the water isdis tilled off leaving a liquid identified as ethylalpha-(benzylmercapto)-propionate. Similarly otheralpha-(benzylmercapto)-esters may be prepared from the correspondingalpha-halo-ester.

EXAMPLE 6 To a suitable reaction vessel equipped with a thermometer andagitator charged with an aqueous solution containing approximately 200parts by weight of water and approximately 16 parts by weight of sodiumhydroxide is added with agitation approximately 49.6 parts by weight ofbenzyl mercaptan. Thereafter a hot ethanol solution containingapproximately 785 parts by weight of ethanol and approximately 85.2parts by weight of alphabromo-propiophenone is added with agitation. Thereaction is exothermic and temperature is permitted to rise. As thetemperature begins to subside approximately 1000 parts by weight ofwater is added with agitation. Thereafter the mass is extracted withmethylene chloride, the extracts combined and subjected to evaporationof methylene chloride. The residue, a solid, isalpha-(benzylmercapto)-propiophenone.

In a similar manner the following precursors of the manufacture of thisinvention are prepared:

alpha- (benzylmercapto)-3,4,5-trichloropropiophenone; alpha-(benzylmercapto -2,4-dibromopropiophenone, alpha- (benzylmercapto)-ortho-bromopropiophenone, alpha- (benzylmercapto)-meta-chloropropiophenone, alphabenzylmercap to) -para-chloropropiophenone,alpha-(benzylmercalpto)-para-bromopropiophenone, alpha- (benzylmercapto)-para-fluoropropiophenone,

employing benzyl mercaptan and the appropriate substituted aeetophenone,for example:

alpha-chloro-3,4,S-trichloropropiophenone,alpha-bromo-Z,4-dibromopropiophenone,alpha-bromo-orthobromopropiophenone,alpha-chloro-ortho-fluoropropiophenone,alpha-chloro-meta-chloropropiophenone,alpha-chloro-para-chloropropiophenone,alpha-bromo-para-bromopropiophenone,alpha-chloro-para-fluoropropiophenone, and

the like, in the presence of a hydrogen halide scavenging agent.Likewise trihalomethyl, alkyl, dialkyl and trialkyl substituted phenonesand higher aromatic ketones can be prepared by the above-describedmethods and used in the manufacture ofalpha-chloro-alpha-aroyl-methane-sulfenyl chlorides and intermediaryproducts by the method of the present invention.

EXAMPLES 7 THROUGH 14 These examples illustrate the preparation ofsubstituted alpha-chloro-methane-sulfenyl chlorides of the formula bythe process of the present invention.

EXAMPLE 7 This example is illustrative of the preparation of ethyl alpha(chloromercapto) alpha-chloropropionate from ethylalpha-(benzylmercapto)-propionate and sulfuryl chloride.

To a suitable reaction vessel equipped with a thermometer, agitator andventing means is charged approximately 22.4 parts by weight of ethylalpha-(benzylmercapto)- propionate dissolved in approximately 275 partsby weight of methylene chloride. While agitating the so-charged mass atabout 0 C. is slowly added approximately 50 parts by weight of sulfurylchloride. The reaction is exothermic and the temperature during theaddition is permitted to rise to about 20 C. Upon completion of thesulfuryl chloride addition the mass is agitated for about one hour atabout room temperature. Thereafter the mass is stripped of volatilesunder vacuum to give a liquid residue [composed chiefly of an equimolarmixture of ethyl alpha-(chloromercapto)-alpha-chloropropio nate andby-product benzyl chloride] which residue is fractionally distilled andthe yellow liquid collected at -86 C. at 13 mm. of mercury is identifiedas ethyl alpha-(chloromercapto)-alpha-chloropropionate.

EXAMPLE 8 EXAMPLE 9 The procedure of Example 7 is followed except thatin place of 22.4 parts by weight of ethylalpha-(benzylmercapto)-propionate an equimolecular proportion of ethylalpha-mercaptopropionate is charged to the reaction vessel. The use ofethyl alpha-mercapto-propionate simplifies the purification of theresultant ethyl alpha-(chloromercapto)-alpha-chloropropionate which isobtained as a product because the formation of liquid by-products isminimized by this procedure.

EXAMPLE The procedure of Example 8 is followed except that in place ofethyl alpha-(benzylmercapto)-propionate an equimolecular proportion ofethyl alpha-mercapto-propiomate is charged to the reaction vessel. Asnoted in Example 9 the purification of the resultant product ethylalpha- (chloromercapto)-alpha-chloropropionate is simplified because theformation of liquid by-products is minimized by this procedure.

In similar fashion other alpha-(chloromercapto)-alphachloro esters maybe prepared from the corresponding alpha-mercapto-esters and chlorineand/or sulfuryl chloride.

EXAMPLE 11 To a suitable reaction vessel equipped with a thermometer,agitator and venting means is charged approximately 23 parts by weightof alpha-mercapto-ortho-chloropropanilide dissolved in approximately 200parts by weight of methylene chloride. While agitating the sochargedmass at about 0 C. is slowly added approximately 43 parts by weight ofsulfuryl chloride The reaction is exothermic and the temperature duringthe addition is permitted to rise to about C. Upon completion of thesulfuryl chloride addition, the mass is agitated for about two hours atabout room temperature. Thereafter, the mass is stripped of volatilesunder vacuum to give a solid residue which residue is dissolved inpetroleum ether solvent, crystallized by cooling the solution to about70 degrees centigrade, separated from the solvent by filtration andidentified as alpha-chloro-alpha-(chloromercapto -ortho-chloropropanilide.

Alpha-chloro-alpha-(chloromercapto) ortho chloropropanilide exhibitspre-emergent herbicidal activity against cocklebur and velvet leaf.

EXAMPLE 12 This example illustrates the preparation ofalpha-chloro-alpha-(chlorornercapto)-ortho-chloropropanilide fromalpha-mercapto-ortho-chloropropanilide and chlorine.

The procedure of Example 11 is followed except that the reaction iscarried out under reflux and instead of charging to the system 43 partsby weight of sulfuryl chloride, chlorine gas is bubbled through therefluxing mass until approximately 23 parts by weight thereof isabsorbed. Alpha-chloro-alpha (chloromercapto)-orthochloropropanilide isobtained.

In similar fashion other alpha-(chloromercapto)-alphachloro anilides maybe prepared from the corresponding alpha-mercapto-anilides and chlorineand/or sulfuryl chloride.

EXAMPLE 13 The procedure of Example 11 is followed except that in placeof alpha-mercapto-ortho-chloropropanilide an equimolecular proportion ofN,N-di-ethyl-alpha-mercaptopropionamide is charged to the reactionvessel. N,N-diethyl-alpha-chloro-alpha (chloromercapto)-propionamide isobtained.

EXAMPLE 14 The procedure of Example 12 is followed except that in placeof alpha-mercapto-ortho chloropropanilide an equimolecular proportion ofN,N-di-ethyl-alpha-mercapto-propionarnide is charged to the reactionvessel. N,N-diethyl alpha chloro-alpha(chloromercapto)-propionamide isobtained.

In similar fashion other alpha-(chloromercapto)-alphachloro-amides maybe prepared from the corresponding alpha-mercapto-amides and chlorineand/or sulfuryl chloride.

10 EXAMPLES 15 THROUGH 19 These examples illustrate the preparation ofsubstituted alpha-chloromethane-sulfenyl chlorides of the formula 01E"--C(5SC1 O RCHOl by the process of the present invention.

EXAMPLE 15 To a suitable reaction vessel equipped with a thermometer,agitator and venting means is charged approximately 25.6 parts by weightof alpha-(benzylmercapto)-propiophenone dissolved in approximately 300parts by weight of 1,2 dichloroethane. While agitating the so-chargedmass at about 0 C. is slowly added approximately 30 parts by weight ofsulfuryl chloride. The reaction is exothermic and the temperature duringthe addition is permitted to rise to about 20 C. Upon completion of thesulfuryl chloride addition, the mass is agitated for about three hoursat about room temperature. Thereafter, the mass is stripped of volatilesunder vacuum to give a liquid residue which residue is dissolved inpetroleum ether solvent, crystallized by cooling the solution to about70 degrees centigrade, separated from the solvent by filtration andidentified as alpha-benzoyl-alpha-chloro-alpha- (chloromethy1)-methanesulfenyl chloride.

Alpha-benzoyl alpha chloro-alpha-(chloromethyl)- methane sulfenylchloride was observed to be active as a pre-emergent herbicide tosmartweed and velvet leaf.

EXAMPLES 16- THROUGH 18 The procedure of Example 15 is followed exceptthat in place of alpha-(benzylmercapto)-propiophenone in the amount ofabout 25.6 parts by weight, a substituted alpha-(benzylmercapto)-propiophenone as shown in column A is added in anamount such that the molecular proportion of substitutedalpha-(benzylmercapto)-propiophenone to sulfuryl chloride is 1 to 3. -Bythis method, the corresponding substitutedalpha-chloro-alpha-(chloromercapto)-propiophenone is prepared as shownin column B.

No. A

16. Alpha-(benzylmercapto) para-chloropropiophenone.

17- Alpha-(benzylmercapto)-para-bromoproprophenone.

18.. Alpha-(benzylthio)- para-fluoroproplophenone.

Alpha-chloro-alpha-(para-chlorobenzoyl)-alpha-(chloromethyl)-methane-sulfenyl chloride.

Alpha-chloro-alpha-(para-bromobenzoyl)-alpha-(chloromethyl)-methane-sulfenyl chloride.

Alpha-chloro-alpha-(para-fiuorobenzoyl)-alpha-(chloromethyl)-methane-sulfenyl chloride.

EXAMPLE 19 EXAMPLE 20 This example illustrates the preparation ofintermediary products of the formula from the correspondingalpha-(benzylmercapto)-propiophenone and sulfuryl chloride.

To a suitable reaction vessel equipped with a thermometer, agitator andventing means is charged approximately 25.6 parts by weight ofalpha-(benzylmercapto)- propiophenone dissolved in approximately 275parts by weight of methylene chloride. While agitating the sochargedmass at about C. is slowly added approximately 13.4 parts by weight ofsulfuryl chloride. The reaction is exothermic and the temperature duringthe addition is permitted to rise to about 20 C. Upon completion of thesulfuryl chloride addition, the mass is agitated for about one hour atabout room temperature. Thereafter, the mass is stripped of volatilesunder vacuum to give a liquid residue, which residue is dissolved inpentane, crystallized by cooling the solution to about --70 de greescentigrade, separated from the pentane by filtration and identified asalpha-(chloromethyl)-alpha-(benzylmercapto)-acetophenone.

In similar fashion, substituted alpha-(chloromethyl)-alpha-(benzylmercapto)-acetophenones can be prepared from thecorresponding substituted alpha-(benzylmercapto) -propiophenones.

EXAMPLE 21 EXAMPLE 22 This example illustrates the preparation ofintermediary products of the formula To a suitable reaction vesselequipped with a thermometer, agitator and venting means is chargedapproximately 22.4 parts by weight of ethylalpha-(benzylmercapto)-propionate dissolved in approximately 275 partsby weight of methylene chloride. While agitating the socharged mass atabout 0 C. is slowly added approximately 13.4 parts by weight ofsnlfuryl chloride. The reaction is exothermic and the temperature duringthe addition is permitted to rise to about 20 C. Upon completion of thesulturyl chloride addition the mass is stripped of volatiles undervacuum to give a liquid residue which residue is purified byconventional means and is identified as ethylalpha-(benzylmercapto)-alphachloropropionate.

EXAMPLE 23 This example illustrates the preparation of ethyl alpha-(benzylmercapto) alpha chloropropionate from ethylalpha-('benzylmercapto)-propionate and chlorine.

The procedure of Example 22 is followed except that the reaction iscarried out under reflux and instead of charging to the system 13.4-parts by weight of sultu'ryl chloride, chlorine gas is bubbled throughthe refluxing mass until approximately 7.1 parts by weight thereof isabsorbed. Ethyl alpha (benzylmercapto)alpha-chloropropionate isobtained.

In similar fashion other alpha-(benzylmercapto)-alpha chloro-esters maybe prepared from the corresponding alpha- (benzylmercapto -esters.

12 EXAMPLE 24 The procedure for testing pro-emergent herbicidal activityof representative substituted alpha-chloro-methanesulfenyl chlorides ofthis invention and their precursors and intermediaries is as follows:

A good grade of top soil is placed in aluminum pans and compacted to adepth of to /2 inch from the top of the pan. A pre-determined number ofseeds of each of several plant species are placed on top of the soil inthe pans. The seeds are covered with soil and the pans leveled. Theherbicidal composition is applied by spraying the surface of the toplayer of soil with a solution containing a sutficient amount of activeingredient to obtain a rate of application of 5 lbs. per acre. The pansare then placed on a sand bench in the greenhouse and watered from belowas needed. The plants are observed at the end of approximately 14 daysand the results recorded.

What is claimed is:

1. A substituted alpha-chloro-methane-sulfenyl chloride having theformula wherein R is hydrogen or 'alkyl of 1 through 3 carbons and E" isselected from the group consisting of phenyl, tolyl, dimethylphenyl,ethylphenyl, diethylphenyl, trimethylphenyl, triethylphenyl,propylphenyl, cumenyl, trihalomethylphenyl, halophenyl, dihalophenyl andtrihalophenyl.

2. A compound of claim 1 wherein R is hydrogen.

3. A compound of claim 2 wherein E" is halogenated aryl.

4. The compound of claim 2 wherein E" is phenyl.

5. A method for the preparation of a substitutedalphachloro-methane-sultenyl chloride of the formula 0 c1 E" "3( 7 5 ClRGHCI from a corresponding precursor of the formula wherein E" is arylselected from the group consisting of phenyl, tolyl, dimethylphenyl,ethylphenyl, diethylphenyl, trimethylphenyl, triethylphenyl,propylphenyl, cumenyl, and trihalomethylphenyl or halogenated arylselected from the group consisting of halophenyl, dihalophenyl andtrihalophenyl and R is hydrogen or alkyl of from 1 through 3 carbonswhich comprises mixing said precursor with at least the stoichiometricamount of a chlorinating agent which is a member of the group consistingof chlorine, sulfuryl chloride and mixtures thereof and heating saidmixture whereby evolution of hydrogen chloride is eifected.

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